Specimen grips



13,1959 .L c. McvLELLAND l y 2,908,163 l l f l I SPEIMEN GRIPS(5 Filed Oct. 28,

s sneetssne'et 1 ATTORNEY INVENTOR Y J. MGCLELLND y 2,908,163

ou. 13, V195s SPECIMEN' GRIPS Filed Oct. `28.1957

, l. 4 Y Y\\\\\\\\\\\\\\\sel. v S A\|H|\\| A 6 H United States Patent() ice SPECllVlEN GRIPS John' C. McClelland, Flourtown, Pa., assignor to Tatuall Measuring Systems Company, Philadelphia, Pa., a corporation 'of Delaware Application October 28, 1957, Serial No. 692,930

4 Claims. (Cl. 73-103) This invention relates to specimen grips, especially for testing machines, and has for an object the provision of improvements in this art.

One of the particular objects is to provide grips which act rapidly and effectively to grip a specimen.

Another object is to provide grips which furnish free access from the front for the insertionfand removal of specimens.

Another object is to provide grips which retain the ends of a specimen, broken or otherwise, until released.

Another object is to provide grips which are free from backlash or loose movement when theloading is reversed asin alternate tension and compression testing.

Another object is to provide grips which accurately center the ends of the specimen.

Another object is to provide grips which can be quickly assembled land separated.

Another object is to provide grips which are simple and inexpensive and which can readily be applied to existing machines.

The above and other objects and advantages will be apparent from the following description of an exemplary embodiment, reference 'being made to the accompanying drawings wherein:

Fig. l is a front elevation of a testing machine having grips which embody the present invention;

Fig. 2 is an enlarged elevation and vertical section of Y the upper grip mechanism of the machine; the section being taken on the line 2-2 off Fig. 4;

Fig. 3 is a vertical section taken on the line 3-3 of Fig. 4;

Fig. 4 is a horizontal section taken on the line 4-4 ot Fig. 2; Y Fig. 5 is an enlarged front elevation of the grip shown in Fig. 4;

Fig. 6 is 'a left side elevation of the parts shown in Figs.

4 and 5;

Fig. 7 is a right side elevation of the parts shown in Figs. 4 and 5; and

Fig. Sis a wiring diagram.

In Fig. 1, a complete testing machine is shown to illustrate how the grips of the present invention are used thereon. It comprises a base 10, Ia table 1.1, columns 12, a movable crosshead 13, a top column-connecting 'beam 14, and rams |15 which have movable cylinders to raise and lower the table, the pistons being secured to the columns which are anchored to the base. The crosshead can be secured at any point alongy the columns.

Upper and lower grips 16, with which the present invention is particularly concerned, are secured to the crosshead 13 and table 1:1 respectively. The grips are alike but are reversed in position so the description of one will serve for both.

A load cell unit v17 carried by the crosshead measures the strains in the specimen. As shown in Fig. 2, the upper grip is Isecured to the load cell by spaced ilexible plates 18 and 19, an intermediate spacer 20, and securing uid line 52 suitably connected to the bag as by being' vulcanized thereto or secured by a nipple.

engagement of the grip blocks with the edges of the open-v j '2,908,163 Patented Oct. 413, 1959.

intermediate spacers 33 keyed in position by recessed key bars 34 and edge connecting plates 35 and 36 secured by headed screws 37. The edge plate 35 is firmly held in position by keys 38 extending around its periphery at a distance from the edges. The upper and lovver plates 31 and 32 are rigidly secured together by bolts 39.

The upper and lower plates 31 and 32 and the spacers .p33 form between them a transverse guideway for the gripping mechanism which here includes rough faced grip blocks 42 and pusher I`blocks 43 therebehind. The blocks are tapered on their engaging surfaces so that when a specimen is gripped the grip blocks will be pressed upward against the top plate 31 and the pusher blocks will be pressed down against the lower plate 32. This avoids all backlash or loose movements when the loads are rel versed.

The grip lblocks and pusher blocks are loosely entrained by headed screws 44 threaded in one block which t loosenly in oversized holes of the companion block. This provides that the grip blocks will be pulled back with` the pusher blocks when the latter are retracted. v

One pusher block -43 is moved in and out to a set index position for each size specimen by any suitable means, such, for example, as a screw 4S which is threaded in the side plate 36 and which has a retaining turn tit of its head 46 in an undercut recess in the pusher block.

The other pusher block 43 is moved in by power means,

herek a fluid operated expansi-ble bag '50, and is moved back outward by suitable power means, here shown as lsprings 51, disposed in recesses of cooperating shoulders (Fig. 4) of the pusher block and the spacer blocks 33. A source of pressure -uid is connected to the bag 50 by a tion is shown on the side of the bag but may be made on the back if expansion and contraction of the side should cause any diiculty, such as leakage.

The outward movement of the blocks is limited by e11- ing 53 in the plate 32 through which the ends of the grip blocks project. The Huid bag is prevented from expanding into the spaces around the pusher block by a thin outer sealing frame 54 of angular cross section. The outer edges of the frame expand into contact with the pusher block and guide sides to prevent entry of the bag even when the block is not fitted to close tolerances in the guideway.

Means are provided for gaging the stop position of the manually adjusted blocks so that the specimen will be accurately centered transversely. As shown in Fig. 1, the manual adjusting screw at the top is Aarranged on one side and at lthe bottom is arranged at the opposite side. When the screws are equally adjusted the grip blocks will `stand at equal distances from a vertical central plane running from front to back. By making the total distance of both equal to the transverse width of the specimen the specimen will be disposed in vertical position. To show the setting there is secured alongside each screw a marked gage plate 56 and the end of the screw around its circumference is provided with division markings, as shown in Fig. 7.

The adjustment may be indicated more precisely by having the screws move a slider 58 of a rheostat 59 as they are turned` in and out. By placing these variable rheostat resistances in a bridge circuit, as shown in Fig.l 8, the equality of setting is established when the bridge reading is zero. ln this circuit the upper and lower gripresistors-y 59 are respectively', inditzated:as'RAll,Y ar'idffRZ-ad the standard resistances of thebridgelarej id'ieatedlas R3;` and R4." The'slideris moved byy ahead,

yMeans are provided for adjusting theppositionof the backedge of the specimen attop .-andbottomtaassure Hnge ,60,` secured to ,the end of the screw.

tbattlie'ibackA edgeis disposedvertically; The Vmeans.

heeiri'showncomprisescrew gages secured to the grip; holder'. at the rear center. and scalefis providedas on micrometers.

untilit" is broughtintocontact withthe adjustable back A Vernier adjustment- Tle.A front of.. the grip framesis open, lasfshown-V. in,- Fi"g.`4,.to.permit. the specimento. bequicldyginserted stops 643'. With ;the.opposite sides, top andbottom, rst

manuallyiadjustedgfor the selected specimen and a specimen linserted againstthe back stops, the uidfbags are simultaneously. ill'ed Ywith pressure fluid and the specirn'enis imm'e'diatelyfgripped.for. testing,V Thespecimen` ends .will beretained until the fluid pressure is relieved andthe. springscause the grip blocks v ononevside'at eachend to retract and release the specimen. l

y:It. is.` thus seen-y that the invention provides simple,

sturdy, reliable.,accurate and-easily` operated means for:

gripping specimens for testing. f v

lWhileone embodimentvhas been described forfpu'rphosesnof illustration it isrto Ybe understood that; there thegeneral scope ofthe invention.

What is claimedis:

v1. -Specimen grips comprising` in combination;y a frame having a transversel guideway, said guideway including spaced upper and lower block-,retaining guide, surfaces,

gripperjaw blocks .slidable along said guidewaytoward and from aspecimen center line, pusher blocks loosely,

entrained with said gripper blocks andfalso .mounted for sliding-movement along said -gu-ideway,` said gripper and pusher. blocks` beingguided by, saidvretaining surfaces above and below and havingh inclined mating surfaces so thattone'will be pushedup against one;of said Iretainmay` be, various embodiments .and modifications within",k

moving means for the pusher' block on the other side comprises a power operated device for moving it inward, and springs for moving it outward.

3. Specimen grips comprising'in combination, -a frame having a transverse guideway, said guideway including spaced upper and lower block retaining guide surfaces, gripper jaw blocks slidable along said guideway toward and from a specimenfcentenline, pusher blocks loosely entrained with said gripper blocks and also mounted for sliding'movementalong said guideway, said-gripper a-nd pusher blocks-being-guided by said'retainingW surfaces above and below and'having inclined'mating surfaces S0 therme-,will be .pushed'up against, one.; of saidretaining surfaces and the other will be pushed down against the other of said lretaining surfaces when clamped on a specimen;V and means for moving said pusher blocks in and out, spaced grips being provided forropposite ends ofaspecimen, settable adjusting `mea-ns fo'rytlixe;y pusher blocksf atoppositesidesr at opposite ends; and; power means at opposite ends for opera-tingthe` OikllelPusher-fV blocks at'oppositek sides.v i

4. Specimen 'grips` comprising inucombination, a3 framef Vhavingva-transverse guideway, saidaguideway including spaceduppen andlower; block retaining guide surfaees gripper jaw blocks slidable along said Vguidewayf.,toward@ and from I a specimencenter linepusher blocks-.loosely entra-ined wit-h; said gripper blocks'l andyalsoY mounted: forl sliding movement,Y alongsaid; guidewaygsaid gripper andpusher blocks beingguidedby said;retaininglsur.-il faces above f and below and;` having` inclinedmating ,surffaeesso that1oneqwill bepushed up against oneatofrsaid retaining surfaces and theother; will-tbe; pushedidownz` against the other of said retaining surfaces when clamped on a specimen, and means for moving. said Ipusheriblocks`A inland/out, spaced-grips bein-g1 provided foropposite ends Y of afspecimen, settablemadjustingrmeans for'th'eapusher. blocks at opposite sides at opposite ends, andpower means-at oppositeends; foroperatingthe otherpusher blocks,y a-tfk opposite sides; said settable adjusting.Y means at -eachend -being provided-with a rheostat-resistaneell Asetin accordance with the adjusted position.ofsaidupusherV blocks, said rheostatzresistances.being. arranged ina bridge circuit to indicatei when the pusher, blocks and L gripplerblocks4 are: equally spacedfrom afspecimen icenter, line-- atA oppositeends.:

References yCited in thele of-thfispatent UNITED STATES PATENTS 

